The present invention relates to a novel metal-boride based ceramic sintered body having a high density which is suitable as a material for a cutting tool for woodwork and as wear-resistant materials.
Tungsten carbide has been mainly used as material for cutting tools, but there has been a short supply of such raw material recently. Metal borides such as diborides of titanium have mainly been used instead of tungsten carbide.
The metal boride sintered body has high heat resistance, oxidation resistance and strength and hardness at high temperatures, and can be easily obtained from natural resources, but is difficult to sinter and possesses low bending strength as a cutting tool.
The present inventors have already proposed bonding agents for the purpose of improving the sinterability and the bending strength of metal boride sintered bodies (Japanese Publication of Examined Patent Application SHO SHO56-41690, Japanese Publication of Examined Patent Application SHO56-45984, Japanese Publication of Unexamined Patent Application SHO54-72779, Japanese Publication of Unexamined Patent Application SHO56-23246 and Japanese Publication of Unexamined Patent Application SHO56-32379), and certain advantageous effects resulted from the use of these bonding agents. Therefore, the present inventors have further developed materials for improving the heat resistance, the hardness and the bending strength and have developed a material wherein at least one of a metal monoboride and diboride such as Ti, Cr, V, Ta, Nb, Mn, Mo, Hf, Al and Zr as the basic component, and at least one metal component selected from a metal carbide and metal nitride,is combined with the basic component and then sintered (Japanese Publication of Unexamined Patent Application SHO57-42578).
The material has satisfactory properties as a wear-resistant tool, but also has unsatisfactory toughness as a cutting tool for woodwork. Therefore, a ceramic-added carbo-titanium nitride was developed (Japanese Publication of Unexamined Patent Application SHO6l-97169). However, it is further necessary to improve the shock resistance of such materials to enable their wide use as cutting tools.